Bang Kachao, the largest green area in the Bangkok metropolitan area, delivers significant ecosystem services to sustain society free of charge. It is therefore difficult to achieve socially optimal services because of inefficient allocation of resources, over-consumption, and negative externalities resulting from market failures. This study’s purpose is to assess consumers’ willingness to pay (WTP) for enhancing ecosystem services from the Bang Kachao Green Area and to investigate factors influencing the WTP of Bangkok residents. A choice experiment was applied by interviewing 200 respondents living in the Bangkok metropolitan area. The data were collected between July and September 2016 and analyzed using a conditional logit model. The results reveal that the respondents are willing to pay 42 USD per year to improve the ecosystem services in Bang Kachao. The respondents demand clean air the most, followed by food, recreation, and bird diversity. The government of Bangkok may take proactive steps to promote agroforestry and ecotourism in Bang Kachao. A Payment for Ecosystem Services (PES) scheme may ensure the provision of ecosystem services in Bang Kachao.

In subsistence economies where cash is scarce, non-monetary numeraires can be used instead of cash as utility measures. In this study, we investigate the values of the Thai water onion (Crinum thaianum) (WO), an endangered native wetland plant, for each service enhancement in Thailand, by using willingness to pay (WTP) money and willingness to volunteer (WTV) to measure the value of WO habitat conservation outcomes, including biodiversity, water quality, upstream conditions, and recreational opportunities. This study employs choice experiment (CE) surveys and face-to-face interviews with villagers in the WO areas of Phangnga and Ranong provinces in southern Thailand. The results show that improved upstream conditions are the most important benefit for residents, followed by biodiversity and water quality. Improving upstream conditions, biodiversity, and water quality from low to high would increase estimated annual welfare by USD 89 per person, while local residents would also provide an annual WTV of 80.2 days per person in exchange for considerable improvements in upstream conditions, biodiversity, and water quality. We found that low-income people are more likely to provide labor to improve ecosystem services. Overall, the findings suggest that the labor value, just as the monetary value, can also be used to evaluate the preferences for increased ecosystem services. This study implies that employing volunteer labor as a means of payment for accurate welfare estimations might be a practical alternative, and also allowing respondents to indicate their WTV may lead to an increase in the estimated value of ecosystem services.